This is Steven Salzberg's blog on genomics, pseudoscience, medical breakthroughs, higher education, and other topics, including skepticism about unscientific medical practices. Here's where I can say what I really think about abuses and distortions of science, wherever I see them.

People who worry about eating healthy food (and who doesn't?) have recently been very worried about genetically modified organisms, or GMOs. Meanwhile, industrial livestock producers feed enormous quantities of antibiotics to cows, chickens, and bigs, as a way to make them grow faster. Which of these practices poses the greater risk?

This one isn't even close. The threat of GMOs pales in comparison to the overuse of antibiotics, which are creating dangerous superbugs that already kill tens of thousands of people each year.

The anti-GMO forces have been making a big push recently to add "GMO" labels to foods. This particularly campaign is based on the hard-to-disagree-with notion that more information is always good. People have a right to know what they're eating, right?

Well, sure. But how many people out there understand what genetic engineering means? How many understand that virtually all the food we eat is genetically modified - including the most wholesome organic foods? Unless you live out in the wilderness eating wild nuts and berries, you're eating plants and animals that have been genetically modified over the centuries by humans, by selecting which ones to plant and breed. The term GMO is meant to refer to something else: precise genetic engineering, designed to alter just one or two genes. This creates genetic changes that are far less dramatic than the ones that turned ancient maize into today's modern corn, for example. Thus the problem with "GMO" label is that it won't inform people unless they have a solid grounding in molecular genetics.

Teosinte is un-modified corn. Not so yummy, is it?

GMO opponents claim that GMOs are bad for you. So far at least, there's no scientific evidence for this claim. If GMOs were so bad, people would be dropping like flies every night after dinner.

But in the world of infectious disease, a different, far more deadly scenario is unfolding. Drug-resistant bacteria are spreading fast. Scientists have been warning for years that we are blindly marching towards an era when people start to die of previously treatable bacterial infections. Antibiotics, one of the greatest technological advances in the history of civilization, are losing their effectiveness.

Last week, the Washington Postreported that "nightmare bacteria" are real and on the rise. In the U.S. alone, over 23,000 people died last year as a result of drug-resistant bacterial infections, according to the CDC. The CDC report implicated the use of antibiotics in animals as one of the primary causes.

"There has been an appalling lack of progress. The failure to act by the USDA and FDA, the lack of action or concern by Congress, and continued intransigence of the animal agriculture industry have made all of our problems worse."

Can the FDA regulate antibiotics in livestock? Not really, thanks to intensive lobbying by industry. One of the authors of the Hopkins report commented that the FDA is “almost pleading with industry to make voluntary changes.”

But industry isn't going to do this on their own, and so far the government has been utterly ineffective. The study points out that:

"Congress has killed every effort to restrict the feeding of farm animals the same antibiotics used in human medicine ... even as antibiotics have grown less effective in treating infection."

So listen up, GMO alarmists: you're protesting the wrong thing. If you really want people to eat healthier food, start raising Cain over the use of antibiotics in livestock. If you want labels on our food, insist on labels showing whether our food animals were raised antibiotic-free. Stop worrying about a hypothetical fear of a few genetic changes in soybeans, and worry instead about the very real rise of superbugs. You're right to worry about how we raise our food - you're just looking in the wrong place.

Someone finally figured out how to rate surgeons. Don't expect to see a ranking list any time soon, though, the ranking technique was only used for a very small group of specialized surgeons. But boy, does it work well.

"Few studies have directly assessed the technical skill of practicing surgeons, and to our knowledge none have linked the level of surgical skill to clinical outcomes."

They then proceeded to do exactly this. Here's how the study worked: a group of surgeons filmed themselves performing gastric bypass surgery, and submitted one video for review. A team of other surgeons then viewed the tapes and ranked the skill of the surgeons. A least 10 evaluators ranked each video.

After doing the rankings, they followed up by looking at actual surgery results of gastric bypass surgeryon 10,343 patients by these same 20 surgeons, between 2006 and 2012.

The differences between the most skilled and least skilled surgeons were remarkable. Comparing the top 25% to the bottom 25%, Birkmeyer and colleagues found:

The least-skilled surgeons had nearly triple the rate of complications, 14.5% versus 5.2%.

Although death is a very rare outcome for gastric bypass surgery, patients had a higher risk of dying if their operation was done by the least-skilled doctors, 0.26% versus 0.05%.

Across the board, the most skilled surgeons had better results. This shouldn't be surprising, as Birkmeyer and colleagues wrote:

"Few surgeons would be surprised that technical skill is an important determinant of outcomes in patients who have undergone laparoscopic gastric bypass. The procedure is technically complex and performed in patients with morbid obesity, for whom surgical exposure is often challenging."

We know how to rate physical abilities in sports - the top teams and players compete directly against one another. We know that Rafael Nadal and Novak Djokovic are two of the world's best tennis players, even if some people argue about which one deserves to be number 1 (right now it's Nadal). We can argue about the best soccer team, or American football team, or golfer, but eventually we can see for ourselves by watching them perform.

But in the world of medicine, finding out who is best - or even good - is nearly impossible. You can find the best hospitals; U.S. News has a ranking for hospitals, ranked on a published list of criteria (Johns Hopkins Hospital is No. 1). But not the best doctors.

Not surprisingly, people and institutions have tried to create rankings of top doctors. The only ones I'm able to find are based on surveys, such as Castle Connolly. A survey, though, is more a popularity contest than a real measure of how good a doctor is. Many publications offer lists such as the "Top Doctors" lists in New York Magazine or Washingtonian magazine, but these too are just surveys.

One could use outcome measures: shouldn't the best surgeons (and other doctors) have the best results? Yes, of course they should - but we don't know how to measure this, because results depend on how sick the patient was to begin with, whether the patient follows his/her treatment program, etc. Outcome measures tend to make doctors in educated, affluent areas look better, simply because the patients are healthier.

And just imagine: if we had accurate rankings, then the best surgeons could charge more. The worst surgeons (and someone has to be worst) would face pressure to improve their techniques or find another specialty, which would be good for patients. I imagine that plenty of patients would be happy to pay more for a better surgeon. Hospitals do charge dramatically different rates, but not necessarily based on the skill of their doctors.

I don't know about you, but if I need surgery, I want one of those surgeons in the top 25% operating on me. I just don't know how to figure out who they are. Birkmeyer's study shows how we might change that.

I used to take vitamin supplements almost every day. Taking vitamins seems like a good idea: after all, we know that vitamins are essential for life, and vitamin deficiencies can definitely hurt you. I always thought that vitamins were an inexpensive way to get a little bit healthier.

Millions of Americans apparently agree with me. Close to half of the population in the U.S. takes vitamins, with multi-vitamins being the most popular.* Vitamins are sold in virtually every grocery store, ranging from mega-markets like Wegmans to the organic Whole Foods chain.

The vitamin and supplements industry, which is immensely profitable, relies on the intuition that if a little bit of something is good for you, a bit more can't hurt. Right?

Wrong. If you don't have a serious vitamin deficiency, taking supplemental vitamins doesn't provide any benefit, in almost all cases that have been studied. What's even more surprising is this: routinely taking mega-doses of vitamins might actually harm you.

So here are the top 5 vitamins that you should not take (unless your doctor recommends it):

1. Vitamin C. Perhaps the most popular single vitamin supplement, vitamin C occurs in plentiful amounts in many fresh fruits and vegetables. In the early days of global exploration, sailors often died from scurvy, caused by the lack of vitamin C. Way back in the 1700's, Scottish doctor James Lind famously conducted an experiment that proved that citrus fruit cured scurvy, although vitamin C itself wasn't discovered until the 1930s.

Vitamin C gained its current popularity through the woefully misguided efforts of Linus Pauling, who published a book in 1970 recommending mega-doses of C to prevent the common cold. Although Pauling was a brilliant chemist (and Nobel laureate), he was completely wrong about vitamin C, as Paul Offit explains in detail in his new book, "Do You Believe in Magic?"

Vitamin C doesn't prevent or cure colds. This question has been studied exhaustively: a review in 2005 covering 50 years worth of research concluded that

"the lack of effect ... throws doubt on the utility of this wide practice."

2. Vitamin A and beta carotene. Vitamins A, C, and E are all anti-oxidants, which have been promoted for their supposed anti-cancer properties. The evidence doesn't support this: for example, in a large study supported by the National Cancer Institute*, smokers who took vitamin A were more likely to get lung cancer than those who didn't.
Vitamin A plays an important role in vision, but too much vitamin A can be toxic, causing multiple serious side effects. Perhaps the most famous cases of vitamin A toxicity occurred in early polar explorers, who ate the livers of their sled dogs, not realizing that the livers had excessively high amounts of vitamin A. Antarctic explorer Douglas Mawson barely survived, and his companions died, probably of vitamin A poisoning.

3. Vitamin E. Long touted as an anti-cancer agent, vitamin E is a very popular supplement. A large study last year, of 35,533 men, looked at vitamin E and the risk of prostate cancer. The authors found that the risk of cancer increased for men taking vitamin E. In an even larger review done at Johns Hopkins University, Edgar Miller and Lawrence Appel found that the overall risk of death was higher in people who took vitamin E. The Mayo Clinic summarizes the evidence this way:

"Evidence suggests that regular use of high-dose vitamin E may increase the risk of death from all causes by a small amount."

4. Vitamin B6. The B vitamins, including B6 and B12, are present in many foods, and deficiencies are rare. But taking B6 supplements for a long time can be harmful, as NIH's website explains*:

"People almost never get too much vitamin B6 from food. But taking high levels of vitamin B6 from supplements for a year or longer can cause severe nerve damage, leading people to lose control of their bodily movements."

5. Multi-vitamins. This is the big one. With nearly 40% of Americans taking a multi-vitamin, they must be good for you, right? But a huge study that I wrote about last year, looking at 38,772 women over 25 years, found that the overall risk of death increased with long-term use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc, and copper. Death, one must admit, is a pretty bad outcome.

On the evidence, supplementing your diet with any of these 5 vitamins carries little or no benefit, and may cause you harm. This is why we do science, people. Our intuitions aren't always right: just because a little bit of something is good for you does not mean that a lot of it is even better.

Vitamins don't "boost your immune system," they don't promote joint health, they don't reduce stress, and they don't help prevent colds or other common ailments.

So what should one do? Ignore the marketing, and treat supplements like you would any other medicine: take them with caution. If you are taking regular vitamin supplements, or thinking about it, ask your doctor before doing so.

And by the way, 100 grams of spinach has healthy amounts of vitamins A, C, E, K, several B vitamins, and essential minerals including iron and calcium.

So ditch the vitamins and eat your spinach. Or blueberries. Blueberries are great.

[*The statistics and references used in this article were collected, in part, by the U.S. Centers for Disease Control, the U.S. Department of Agriculture, and the National Institutes of Health, all of which are currently shut down due to the stubborn actions of a minority of Representatives in the U.S. Congress. Thanks, Congress!]